In arthroscopic surgery, a torn or ruptured ligament or tendon may be treated by attaching an end of a tendon or ligament graft to bone. The graft end may be secured to the bone by any of a variety of devices and techniques. One common procedure, for example, involves the replacement of the anterior cruciate ligament (ACL) of the knee. In such operations, a tunnel is typically prepared through the patient's tibia, across the interarticular joint and into the femur. A hamstring tendon graft or a bone-tendon-bone graft may be attached to an implantable graft fixation device or screw or the like which is frequently planted in the femoral tunnel to help anchor one end of the graft therein. The other end of the graft is secured in the bone tunnel in the tibia or otherwise secured to the tibia.
Known configurations of such implantable devices incorporate various methods of mounting the graft. Typically, the method of anchoring a graft to bone is dependent upon whether the graft is made of soft tissue, such as a hamstring tendon graft, or whether a bone-tendon-bone type graft is used. By way of example, one method for ACL reconstruction uses a bone-tendon-bone graft and an interference screw, which may be inserted into a bone tunnel parallel to the bone block of the bone-tendon-bone graft. According to this method, holes are typically drilled in the bone block for passing sutures, which serve to pull the graft through the tunnel and into place. The bone block is then anchored in the bone tunnel by inserting an interference screw in the tunnel adjacent the bone block. The compressive action of the screw threads against the bone block and tunnel walls is intended to anchor the bone block of the graft in place.
Alternatively, ACL reconstruction may be accomplished with a hamstring tendon graft. This type of graft has also been secured in a bone tunnel with an interference screw. In this situation, an interference screw may be wedged between the soft-tissue graft and the bone tunnel to anchor the end of the graft in the tunnel. Soft tissue graft fixation may alternatively be accomplished by placing a pin transversely through the femoral tunnel and through the loop of a hamstring graft which is doubled over the transverse pin. Fixation using the cross pin involves preparation of a bone tunnel for placement of the graft and an additional, transverse bone tunnel for the transversely oriented pin.
U.S. Pat. No. 5,931,840 to Goble et al. discloses a bone fixation device for a ligament anchor system. Goble discloses a two part assembly which includes a threaded footing having a longitudinal passageway which is anchored in a bone tunnel. A graft-holding component is then inserted and seated in the longitudinal passageway which extends through the footing. A threaded insertion tool is used to push and guide the graft holding component, with the graft trailing behind, into the bone tunnel. Thus, the graft material and the shaft of the insertion tool are adjacent to each other as the graft is guided into place. The two-part assembly is connected in the bone tunnel, and the insertion tool is then unscrewed and withdrawn from the tunnel.
Another ligament reconstruction graft anchor apparatus is disclosed in U.S. Pat. No. 5,152,790 to Rosenberg et al. The Rosenberg patent describes an anchor assembly having a rotatable cylindrical ring which is open at its ends and has suture tie slots or openings in the cylindrical ring for attaching a ligament graft thereto with sutures. An end of the rotatable ring is connected to a threaded sleeve having a longitudinal passageway which extends through the sleeve and has openings at both ends. After one or more grafts are sutured to the rotatable ring end of the anchor assembly, a driver instrument is inserted through the opening in the ring and into the opening in the threaded sleeve. The grafts are positioned around the shaft of the driver tool, and the tool is used to guide and drive the assembly into the bone tunnel. When the threaded sleeve is screwed into the bone tunnel, twisting of the cylindrical ring and grafts is minimized, because the ring is rotatable with respect to the threaded sleeve.
Known devices and methods for installing and anchoring soft tissue and bone-tendon-bone grafts suffer from inadequacies which can result in damage to the graft, excess trauma to the patient receiving the graft, and/or an increase in post-operative recovery time. In particular, many known devices and graft fixation methods do not allow for satisfactory tensioning of the graft. For example, when an interference screw is used to anchor one end of the graft in a bone tunnel, the screw typically must be removed in order to adjust graft tension. Such removal can cause the graft to tear. Many prior art fixation devices also cause the flexible graft material to twist upon installation or when tension is adjusted. Twisting of the graft is undesirable because it places unequal stresses on the graft, thereby lessening the probability of successful rehabilitation. Furthermore, some prior art anchor systems hold the graft in a manner which preloads the graft on one side and/or forces the graft to one side or the perimeter of the bone tunnel. When the graft is tensioned with a force which is not axially aligned, or when the graft is held along the perimeter of the bone tunnel, the graft may be subject to abrasion caused by motion of the graft against bone in the tunnel, and in particular at the tunnel exits. In addition, many prior art procedures for inserting and affixing grafts are complex and/or require multiple steps that increase the likelihood of trauma to the patient and may lengthen post-operative recovery and rehabilitation. Prior art methods of affixing implants to bone also tend to be severely constrained by the configurations of the implants, wherein generally only one specific procedure may be used to install an implant.
Thus, there is a need for a graft fixation system and method for reconstructing or replacing a ligament or tendon that overcomes the above-mentioned disadvantages and problems found in prior art devices and methods.